diff options
| author | Benjamin Tissoires <benjamin.tissoires@gmail.com> | 2012-11-14 16:59:15 +0100 |
|---|---|---|
| committer | Jiri Kosina <jkosina@suse.cz> | 2012-11-15 10:07:55 +0100 |
| commit | 774638386826621c984ab6994439f474709cac5e (patch) | |
| tree | 897fb8a15947768f7dc9521027c7c20fe830c1bf /drivers/hid/hid-core.c | |
| parent | ccdd699411b77c463022ebac311eb4a06ca56db4 (diff) | |
HID: fix unit exponent parsing
HID spec details special values for the HID field unit exponent.
Basically, the range [0x8..0xf] correspond to [-8..-1], so this is
a standard two's complement on a half-byte.
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Diffstat (limited to 'drivers/hid/hid-core.c')
| -rw-r--r-- | drivers/hid/hid-core.c | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c index f4109fd657f..f5004e2ca0c 100644 --- a/drivers/hid/hid-core.c +++ b/drivers/hid/hid-core.c @@ -315,6 +315,7 @@ static s32 item_sdata(struct hid_item *item) static int hid_parser_global(struct hid_parser *parser, struct hid_item *item) { + __u32 raw_value; switch (item->tag) { case HID_GLOBAL_ITEM_TAG_PUSH: @@ -365,7 +366,14 @@ static int hid_parser_global(struct hid_parser *parser, struct hid_item *item) return 0; case HID_GLOBAL_ITEM_TAG_UNIT_EXPONENT: - parser->global.unit_exponent = item_sdata(item); + /* Units exponent negative numbers are given through a + * two's complement. + * See "6.2.2.7 Global Items" for more information. */ + raw_value = item_udata(item); + if (!(raw_value & 0xfffffff0)) + parser->global.unit_exponent = hid_snto32(raw_value, 4); + else + parser->global.unit_exponent = raw_value; return 0; case HID_GLOBAL_ITEM_TAG_UNIT: @@ -865,6 +873,12 @@ static s32 snto32(__u32 value, unsigned n) return value & (1 << (n - 1)) ? value | (-1 << n) : value; } +s32 hid_snto32(__u32 value, unsigned n) +{ + return snto32(value, n); +} +EXPORT_SYMBOL_GPL(hid_snto32); + /* * Convert a signed 32-bit integer to a signed n-bit integer. */ |